Rabies is a major public health problem in many countries, especially those in the developing areas, and the control of rabies in animals, and especially in wild carnivores, such as the fox, is integral to the ultimate goal of minimizing the public health significance of this disease. Population reduction of the animals, which has been practiced in the past, has not proved to be an effective wild rabies control technique and the vaccination of carnivores associated with the disease has received increasing interest in recent years.
There have been a number of previous attempts to vaccinate carnivores through the oropharyngeal cavity. Black and Lawson (Can. Vet. J. 14[9], 206, [1973]) were able to orally vaccinate foxes, both silver and red, utilizing the ERA (Trademark) strain of rabies virus grown in primary porcine kidney cells, by introducing the vaccine into the oropharyngeal cavity. The virus utilized in this case was lyophilised and specially set out as "free choice" for the animals to eat. The use of bait is mentioned in this publication, but no description is given as to the type of bait. Black et al [Can. J. Comp. Med., 34, 309 (1970)]indicated methods of oral vaccination by stomach tube and Baer et al (Am. J. Epid. 93, 487 [1971]) indicated in their publication, methods of oral vaccination for grey and red foxes by various routes, such as stomach tube, feeding explosion using a "coyote-getter", and other methods. These authors did not attempt to use baits to disseminate the vaccine. Baer and Winkler (U.S. Pat. No. 4,014,991) disclose the use of a sausage containing vaccine held in a plastic tube inside the sausage as a bait. Debbie et al (Am. J. Epid., 96, 231, [1972]) showed that wild red foxes may be successfully vaccinated by the oral route using an ERA type of vaccine with a titre &gt;10.sup.3.4 mouse intracerebral lethal dose 50 (MICLD.sub.50)/0.03 ml. Steck in published European Patent Application No. 0100752 discloses the use of a high titre vaccine within a container placed in chicken heads as bait for carnivores.
Such prior art procedures suffer from a number of drawbacks in that they require capturing the foxes for administration of the vaccine, the use of high titre unlicensed vaccines and/or permit the administration of only low volumes of vaccine. There exists, therefore, a need for an effective manner of oral administration of vaccines to mammals.